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minute, whereas ten or twenty minutes were often consumed 

 in ramming down gravel or stones. 



Another improvement I have found to be of great value, 

 and this is simply to leave a space between the charge of 

 powder and the tamping stuff ; this space, which of course 

 contains air, has the effect of increasing the action of the 

 powder upon the rock, and also of securing the tamping stuff 

 from all chance of being blown out by the force of the ex- 

 plosion — an accident which frequently happened in the old 

 plan of tamping, to the waste of the entire charge of powder. 

 I can almost venture to assert that, by the use of sand, tamp- 

 ing and the maintainance of a space of twelve or eighteen 

 inches between it and the powder, no charge would blow the 

 sand out unless the rock was absolutely unrendable. The 

 effect of allowing a space to exist between the tamping and 

 the powder, may be exemplified when a bullet is not rammed 

 down upon its charge in a musket, for in this case the firing 

 of the musket seldom drives out the bullet, but will rather 

 burst the barrel ; and were the bullet near the muzzle, a very 

 small quantity of powder would be sufficient to produce this 

 effect. I have heard sportsmen assert that the resistance 

 offered by the mere plugging up for an inch or two of the 

 muzzle of a fowling piece, by so slight an obstruction as 

 snow or soil, has been sufficient to cause the bursting of the 

 barrel. This singular fact is of easy explanation, and its 

 necessary existence can be fully proved by mathematical 

 demonstration, into which it would be out of place to enter 

 at present ; it is sufficient for our purpose to know that in / 

 all blasting operations where these improvements have been 

 carried out — which they have been in many hundred cases — 

 in no one instance has it happened that the tamping stuff has 

 been blown out, prior to the rending of the rock. I call 

 your attention most particularly to these improvements, 

 because they are a source of great security to the work- 



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